swift

b61c51b7 - Fixed clang 4.0 compilation under Arch Linux with icu59.1-1 (#10361)

Fixed clang 4.0 compilation under Arch Linux with icu59.1-1 (#10361) ICU headers prefer use of `char16_t` instead of `uint16_t` for `UChar` in C++, where it is treated as a distinct type. This fixes associated warnings and errors.